Optical gain in wide bandgap GaN quantum well lasers

We investigate the gain characteristics of III - V nitride lasers operating at wavelengths around 400 nm, comparing the transparency and threshold characteristics with both GaAs and GaInP bulk and quantum well laser devices. We find that the calculated threshold carrier density and radiative current density have a stronger dependence on well width, , in GaN-based single quantum well lasers than is the case for either GaAs- or GaInP-based devices, with a relatively sharp minimum predicted in both carrier and current density for of about 3.5 nm. Although the threshold carrier densities are found to be much larger than in typical GaAs lasers, our calculations indicate that nitride-based lasers may compare favourably with current GaInP visible laser devices.